The invention relates generally to internal combustion engines which can be either of the two-stroke or four-stroke type. In addition, the invention relates to fuel feeding systems including systems for enriching fuel flow when the ambient air is below a predetermined temperature (and for discontinuing such fuel enrichment when the ambient air is above the predetermined temperature). Still further in addition, the invention relates to fuel feeding systems for enriching fuel flow when the vacuum condition in the air induction passage is above a predetermined absolute pressure and for discontinuing such enrichment when the vacuum condition in the air induction passage is below the predetermined absolute pressure.